Okay, after rereading the moderators explanation, and doing some experimenting, I think I've got it figured out. Ill try to explain as simply as i can- In reality, we've all been making it harder than it has to be! The main thing to understand is that the app is giving you REAL TIME information based on its PREDICTIONS of how your day will go. It is not like other programs where you have the same calorie budget every day that you subtract from like a checkbook. It adjusts your calorie budget in real time to match the actual number of calories you are burning. Every day is different - so your calorie budget is different each day too.
First, the scale. The scale compares current calories in to current calories out, and tells you whether you are on track SO FAR to make your deficit by the end of the day or not. So if after breakfast the difference between calories in and calories out is only 20 calories, it assumes you are going to continue eating roughly that same way for lunch and dinner too, meaning your total deficit would only be about 60 calories (20 per meal) by the end of the day. Definitely over budget! So the scale goes to red to warn you that you had better either exercise more than usual today, or eat less at the next 2 meals if you want to get back on track. So the red "overbudget" DOES NOT mean you ate all your calories for the day- it means as of right now you are eating too much for what you have burned so far, and IF you continue that pattern you won't make your deficit goal.
If, after breakfast, the difference between in and out is more like 340, then fit bit thinks "keep that up and by dinner we'll be at 1020 deficit- just right!" So it puts you in the green.
Its just a wakeup call, warning you or reassuring you about where you are headed on your current path so you can make adjustments if needed.
Next is the "Calories left" amount. This number has NOTHING to do with the scale numbers! It is the amount that fitbit PREDICTS at the beginning of each day that you can eat and still make your deficit, IF you continue your usual activity. From what I can tell, this prediction comes from your average daily calories burned in the past. It will change slightly every day, as the average adjusts. It's is NOT a fixed calorie budget, like "I get 1600 cal every day". All fitbit cares about is getting your deficit every day, not eating a set number of calories.
For example, my average daily calories burned is about 2800. My chosen deficit is 1000, so this morning before I ate anything, it said "1800 calories left". Makes sense. Where it gets tricky is when that number starts changing without me eating anything!
Here's my explanation for that:
Fitbit expects me to burn my usual 2800 calories. Thats why it gave me 1800 to eat today. But what if I'm having an off day? Not exercising as much as usual? I might only burn 2400 cal that day, and if I still eat 1800, I won't make my deficit. So partway through the day, fitbit notices I'm not as active as usual, and adjusts my "calories left" down a little so that I'll eat less and be more likely to meet my deficit. If I continue to be inactive all day, (like if I'm sick in bed or traveling in a car) then every few minutes fitbit will realize I'm getting farther and farther off track from what it originally expected, and adjust my "calories left" down little by little to nudge me closer to target. So by the end of the day, if i follow the program, i will have only eaten 1400 cal instead of 1800, and ill still reach my 1000 deficit. (Now i may not want to eat that little, and prefer to stick with the 1800 and end up not meeting my deficit that day, and thats okay. But at the end of the day, fitbit will tell me i went over by 400 calories. Even though i had 1800 to start with, by the end of the day i didnt burn as many as hoped, so I could only afford to eat 1400.)
Conversly, if I'm having an awesome day and go for an extra long run that morning, fitbit will realize I'm already on track to burn more than my average of 2800, and will INCREASE "calories left", so I will eat more and still meet the deficit.
All it cares about is the deficit!
Its actually a pretty cool system. It automatically adjusts to your personal activity levels, and gives real time info on how close you are to being on track for your deficit. As you lose weight over time and enter your new weight, your calorie needs and calories burned automatically update into the equation, helping you avoid the confusion that comes with traditional calorie counting, where you reach a plateau and think "1600 calories a day just isn't working anymore, should I eat less or exercise more?...". Also it automatically allows you to eat more on days you work really hard, so you dont make the mistake of getting over hungry and sabatoging yourself.
This program will always steer you toward getting your deficit, no matter the numbers inbolved.
The key is just to trust that it works and not get hung up on the math! If your scale is in the red, walk a little more and go a little lighter on your next meal- it will turn green once you are back on track. If your "calories left" is dropping and it looks like you won't be able to afford dessert like you planned, go for a run to bring them back up. Or only eat half the dessert. And if you are already over because after you ate your last calorie and thought you were okay they rudely kept dropping, you can still go for the evening walk and bring the calories back up before midnight.
It may take some getting used to- last night I had 75 cal left after dinner and was in the green zone- thought I was good. But as the night went on I was very sedentary and the only calories being burned were the basal calories I burn at rest. The "75 left" dropped to 55 then 22... and when I checked the next morning I was actually 4 calories over for the day! Based on my previous average burn, fitbit had expected me to do more activity that evening. But I didnt. And so I didn't make my deficit, even though I ate within what I thought was my calorie budget. Only by 4 calories, so it's not the end of the world. But if I had just taken a few more steps it would have been perfect.
Im having to adjust the way i think about my calorie budget to make this work, and its a little irritating. But that's why this program so accurate and effective- and I think I'm learning to like it. No matter what, it WILL keep me headed toward my deficit, and if I follow, I WILL lose 2lbs a week! 🙂
Hope that helps!
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